基于分子动力学的单层石墨烯纳米压痕模拟研究

发布时间：2018-06-23 11:45

本文选题：石墨烯 + 纳米压痕　；参考：《西安建筑科技大学》2015年硕士论文

【摘要】：通过分子动力学方法,本文模拟了石墨烯的纳米压痕过程,并对其模拟结果进行了分析。首先介绍石墨烯这一新型材料的研发现状及纳米压痕技术的发展背景,其次简述分子动力学基本思想及模拟的基本步骤,并对选择势函数及运动方程的求解算法加以陈述。基于以上理论,建立单层石墨烯纳米压痕模型,用Tersoff势函数描述金刚石内部原子与石墨烯内部原子间的相互作用,用Lennerd-Jones势描述压头原子与石墨烯原子之间的范德华力,用Verlet算法求解原子的运动方程。本文研究了石墨烯在纳米压痕过程中的微观变形机制,探究了载荷-位移曲线在不同加载条件下的变化规律,压头受力和系统势能的变化规律,缺陷石墨烯纳米压痕模拟的微观变形机制,并对不同缺陷类型的模拟结果进行对比分析,研究了完美/缺陷石墨烯纳米压痕过程中的温度效应。研究表明,石墨烯临界载荷与压头半径有密切的关系:压头半径越大,临界载荷越大,相应的压入深度也越大;薄膜半径越大,临界压入深度越大,但临界载荷相差不大。在一定的取值范围内,压头的加载速率越大,它的临界载荷越大,相应的压深越小。当加载速度大于0.05 nm/ps时,加载速度对压痕曲线有显著影响,而当加载速度小于该值时,压痕曲线变化较小。对缺陷石墨烯而言,单/双空位缺陷距离薄膜中心越近,相应的临界载荷越小;同时,不同双空位缺陷中石墨烯薄膜的载荷-位移曲线呈现不同的变化规律。单个SW缺陷基本不影响薄膜的力学性能和变形破坏机制。温度对单层石墨烯的载荷-位移曲线有一定的影响。
[Abstract]:The nanocrystalline indentation process of graphene was simulated by molecular dynamics and the simulation results were analyzed. Firstly, the research and development status of graphene, a new material, and the development background of nano-indentation technology are introduced. Secondly, the basic idea of molecular dynamics and the basic steps of simulation are briefly described, and the selection potential function and the algorithm for solving the equation of motion are described. Based on the above theory, a nanometer-indentation model of graphene monolayer is established. The interaction between the atoms in diamond and graphene is described by Tersoff potential function, and the van der Waals force between the die-head atom and graphene atom is described by Lennerd-Jones potential. The Verlet algorithm is used to solve the equation of motion of atoms. In this paper, the microscopic deformation mechanism of graphene in the process of nano-indentation is studied, and the variation law of load-displacement curve under different loading conditions, the changing law of the pressure on the head and the potential energy of the system are discussed. The microscopic deformation mechanism of nano-indentation simulation of graphene defects was studied. The temperature effect in the process of perfect / defective graphene nano-indentation was studied by comparing and analyzing the simulation results of different defect types. The study shows that the critical load of graphene is closely related to the radius of the head: the larger the radius of the head, the greater the critical load, the greater the corresponding depth of indentation, and the greater the radius of film, the greater the critical depth of indentation, but the less the critical load. In a certain range of values, the greater the loading rate of the head, the greater the critical load and the smaller the corresponding depth. When the loading speed is more than 0. 05 nm/ps, the loading speed has a significant effect on the indentation curve, but when the loading speed is less than this value, the indentation curve changes slightly. For graphene defects, the closer the defect center is, the smaller the critical load is. At the same time, the load-displacement curves of graphene thin films with different divacancies show different changes. The mechanical properties and deformation-failure mechanism of the films are not affected by a single SW defect. Temperature has a certain effect on the load-displacement curve of graphene monolayer.
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O613.71;TB383.1

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